The subject matter disclosed herein relates to electron emission surfaces, such as for use in an electron gun.
In non-invasive imaging systems, X-ray tubes are used in various X-ray based imaging systems, such as radiography, mammography, tomosynthesis, C-arm angiography, fluoroscopy, and computed tomography (CT) systems, as well as others. In such systems, the X-ray tubes function as a source of X-ray radiation. The radiation is emitted in response to control signals during an examination or imaging sequence. Typically, the X-ray tube includes a cathode and an anode. An emitter within the cathode may emit a stream of electrons in response to heat resulting from an applied electrical current, and/or an electric field resulting from an applied voltage. The anode may include a target that is impacted by the stream of electrons. The target may, as a result of impact by the electron beam, produce X-ray radiation to be emitted toward an imaged volume.
In such imaging systems, the radiation passes through an imaging volume or space containing a subject of interest, such as a patient in a medical imaging context (but possibly a piece of baggage, a package, or an article of manufacture in non-medical contexts). A portion of the radiation impacts a digital detector or a photographic plate where the image data is collected. In digital X-ray systems a photodetector produces signals representative of the amount or intensity of radiation impacting discrete elements of a detector surface. The signals may then be processed to generate an image that may be displayed for review. In CT systems a detector array, including a series of detector elements, produces similar signals through various positions as a gantry is rotated about a patient.
In non-imaging systems where radiation may be employed, such as systems for oncological radiation treatment, a source of X-rays (such as an X-ray tube) may be used to direct ionizing radiation toward a target tissue. X-ray tubes used for radiation treatment purposes may also include a thermionic emitter and a target anode that generates X-rays, such as described above. Such X-ray tubes or sources may also include one or more collimation features for focusing or limiting emitted X-rays into a beam of a desired size or shape.